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Commit 9dcf7914 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Will Deacon
Browse files

arm64: kernel: use x30 for __enable_mmu return address 



Using x27 for passing to __enable_mmu what is essentially the return
address makes the code look more complicated than it needs to be. So
switch to x30/lr, and update the secondary and cpu_resume call sites to
simply call __enable_mmu as an ordinary function, with a bl instruction.
This requires the callers to be covered by .idmap.text.

Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 3c5e9f23

arch/arm64/kernel/head.S

+7 −14
Original line number Diff line number Diff line
@@ -675,9 +675,9 @@ secondary_startup: 
	 * Common entry point for secondary CPUs.

	 */

	bl	__cpu_setup			// initialise processor



	adr_l	x27, __secondary_switch		// address to jump to after enabling the MMU

	b	__enable_mmu

	bl	__enable_mmu

	ldr	x8, =__secondary_switched

	br	x8

ENDPROC(secondary_startup)



__secondary_switched:
@@ -716,9 +716,9 @@ ENDPROC(__secondary_switched) 
 * Enable the MMU.

 *

 *  x0  = SCTLR_EL1 value for turning on the MMU.

 *  x27 = *virtual* address to jump to upon completion

 *

 * Other registers depend on the function called upon completion.

 * Returns to the caller via x30/lr. This requires the caller to be covered

 * by the .idmap.text section.

 *

 * Checks if the selected granule size is supported by the CPU.

 * If it isn't, park the CPU
@@ -744,7 +744,7 @@ ENTRY(__enable_mmu) 
	ic	iallu

	dsb	nsh

	isb

	br	x27

	ret

ENDPROC(__enable_mmu)



__no_granule_support:
@@ -789,9 +789,7 @@ __primary_switch: 
	mrs	x20, sctlr_el1			// preserve old SCTLR_EL1 value

#endif



	adr	x27, 0f

	b	__enable_mmu

0:

	bl	__enable_mmu

#ifdef CONFIG_RELOCATABLE

	bl	__relocate_kernel

#ifdef CONFIG_RANDOMIZE_BASE
@@ -822,8 +820,3 @@ __primary_switch: 
	ldr	x8, =__primary_switched

	br	x8

ENDPROC(__primary_switch)
 


__secondary_switch:

	ldr	x8, =__secondary_switched

	br	x8

ENDPROC(__secondary_switch)

arch/arm64/kernel/sleep.S

+2 −6
Original line number Diff line number Diff line
@@ -100,14 +100,10 @@ ENTRY(cpu_resume) 
	bl	el2_setup		// if in EL2 drop to EL1 cleanly

	bl	__cpu_setup

	/* enable the MMU early - so we can access sleep_save_stash by va */

	adr_l	x27, _resume_switched	/* __enable_mmu will branch here */

	b	__enable_mmu

ENDPROC(cpu_resume)



_resume_switched:

	bl	__enable_mmu

	ldr	x8, =_cpu_resume

	br	x8

ENDPROC(_resume_switched)

ENDPROC(cpu_resume)

	.ltorg

	.popsection